docs: 00-INDEX: document directories/files with no docs

There are a number of files/directories that don't contain
any documentation. They're related to ReST file conversion.

As a matter of completeness, since Makefile is also documented
there, add an entry for those files too.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>